Furnace



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FURNACE Original Filed July 21, 1925 2 Sheets-Sheet 2 Patented Jan. 16,1934 UNITED STATES I.PATENT OFFICE FURNACE Thomas (G. Coghllan,

Elizabeth, and Einar A. Johnsen, deceased, late of Mountain Lakes, N.12E., by Sigrid fl. Johnsen, executrix, Erooliriyn, N.

4 (Claims.

This application is a division of a prior application of applicants, S.N. 44,957, led July 21, 1925, on which Patent No. 1,898,479 was grantedFeb. 21, 1933. The novel features of the invention will be bestunderstood from the following description and the annexed drawings, inwhich is shown a selected embodiment and in which;

Fig. 1 is a vertical sectional view througha portion of a furnace andassociated boiler showing the invention applied thereto;

Fig. 2 is a View on the same plane as Fig. 1, but with parts shown insection, this view being on an enlarged scale and showing certainfeatures of the invention;

Fig. 3 is a fragmentary section on the line 3-3 of Fig. 4 illustratingone of the pipe control valves and Fig. 4 is a plan View of the valveshown in Fig. 3.

Referring now to Fig. 1,- there is shown therein a furnace having alower combustion chamber l and an upper combustion chamber 2 connectedby a restricted throat 3. In the lower part of the g chamber 1 is a fuelburning means exemplied by a chain grate 4, to which fuel is suppliedfrom a hopper 5.

Gases from the upper chamber 2 pass upwardly through a pass 6 downwardlythrough a pass 7 and again upwardly through a pass 8 to an outlet 9.Extending across the threelpas'ses are water tubes 10 connected atopposite ends to headers and inclined slightly to the horizontal in amanner well known in the art. Above the passes 6 and 7 is disposed asuperheater l1. After reaching the outlet 9, thegases are `conductedthrough an air heater 12, and the air from this heater may be suppliedto the furnace in a manner more fully described in the said copendingapplication'.

The dust contained in the gases as they pass over the boiler tubes andthrough the air heater may contain a considerable amount of unburnedfuel, and it is desirable to return such fuel to the fuel bed. In theillustrated embodiment this is r laccomplished by providing a hopper 13beneath the lower edge of the baffle which separates the passes 7 and 8and another hopper 14 in the air heater. These hoppers, particularly thehopper 13, are so placed as to collect dust which may be precipitated bythe gas stream when it changes "0 its direction as beneath the loweredge of ythe baffle.

Leading from the bottoms of the hoppers 13 and.l4 are pipes 15 and 16which are joined to- K gether at the junction 17, and the dust flowing5' through these pipes is conducted by a third pipe (ci. irc-its) 18through an arch 19 over the lower part of the grate 4, so that it willbe deposited upon the fuel bed on this grate. The fuel on the rear partof the grate is burned under the arch 20 to a great extent and,preferably, the supply of air to the lower portion of the grate is suchas to cause an excess of oxygen, whereby the dust or more accurately thefuel in the dust may be thoroughly burned.

Referring now more particularly to Fig. 2, we have shown the pipe 18V asbeing reduced at 21 to form a throat or portion of restrictedcrosssectional area to increase the velocity of the stream of dustflowing therethrough. On the side of the throat away from the furnacechamber is disposed the discharge opening 22 from the pipe 17, andbetween this discharge opening and the throat is disposed a nozzle 23 ona pipe 24 which is connected to a suitablesource of hot air.Conveniently this air may be supplied from the air heater l2, thedetails of thevconnection thereto being omitted, as that is only oneexamy ple of a suitable source of hot air. The hot air passing throughthe pipe 24 is normally under pressure, as is usually the case with hotair being supplied to a combustion chamber, and its velocity isincreased as' it passes through the nozzle 23, and this velocity isstill further increased at the throat 21. In otherwords, the nozzle 23forms an aspirating tube to draw the stream of dust from the dischargeopening 22 and to increase its velocity and, consequently, its pressure.

The pressure by this arrangement is increased enough to overcome thepressure in the charnber l.

The pipes 1'5, 16 and 24 are preferably provided withl suitable slidevalves 25, 26 and 27 respec- 'a steam boiler arranged above saidcombustion chamber, a dust settling chamber below a rear portion of saidsteam boiler in a position to receive dust separating out from theproducts of combustion flowing through said boiler from said combustionchamber, and means for returning collected dust from said settlingchamber in suspension in an air stream to the space in lsaid combustionchamber between said arch and the rear portion of said grate.

2. A steam generator having lower and upper combustion chambers, frontand rear combustion arches extending over said lower chamber andarranged to form a restricted throat between said lower and upperchambers, a traveling fuel grate in said lower chamber having its fuelfeed end extending below said front arch and its ash discharge endextending below said rear arch, a steam boiler arranged above said upperchamber, a dust settling chamber below a rear portion of said steamboiler in a position to receive dust separating out from the products ofcombustion owing through' said boiler from said upper cornu bustionchamber, and means for returning c ollected dust from said settlingchamber in suspension in an air stream to the space in said lower'chamberbetween said rear arch and th rear portion of said grate. K

3. A steam generator having lower and upper combustion chambers, frontand rear combustion arches extending over said lower chamber andarranged to form a restricted throat between said lower and upperchambers, a progressive feed fuel grate in'said-lower chamber having itsfuel feed end extending below said front arch and its ash discharge endextending below said rear arch,

means for passingl air for combustion upwardlyL through the fuel bed onsaid grate with an excess of air above the rear portion of said grate, asteam boiler arranged above said upper chamber, a dust hopper below larear portion of said steam boiler in a position to receive dustseparating from the products of combustion flowing through said boilerfrom said upper combustion chamber, and means under pressure from saidlower chamber said hopper to the 4space in between said rear arch andfor returning collected dust the rear portion of said grate comprising adust conduit connected to said hopper and opening to said lower chamberthrough said rear arch, and a iiuid ejector arranged to discharge intosaid conduit towards said lower chamber to convey the dust therein underan increased pressure into said lower chamber. k

4. A steam generator having lower and upper combustion chambers, arelatively short front arch and a relatively long rear combustion archextending over said lower chamber and arranged to 4form a restrictedthroat between said lower and upper chambers, a chain grate in saidlower chamber having its feed end extending below said front arch andits ash discharge end extending below said rear arch, means for passingair for combustion upwardly through the fuel bed on said grate with anexcess of air above the rear portion of said grate, a bank of boilertubes arranged above said upper chamber, a dust hopper below a rearportion of said tube bank in-a position to receive dust separating fromthe products of combustion owing through said boiler from said uppercombustion chamber, means for returning the collected/dust underpressure from said hopper to the space in said lower chamber betweensaid rear arch and the rear portion of said grate comprising a dustconduit connected to said hopper and opening to said lower chamberthrough said rear arch, an air ejector arranged to discharge into saidconduit in the di- Y,

rection of flow, and a ow constriction in said conduit arranged toincrease the pressure of the air anddust mixture before said mixture mayenter said lower chamber.

THOMAS G. COGHLAN. SIGRID A. JOHNSEN, Eecutri ofthe Estate of Einar A. Johnsen.

